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Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Natacha Rosa, Fernão D. Magalhães, Ricardo Simões and António Torres Marques
Natacha Rosa3nd Year Mechanical Engineering PhD
Student
Enhanced Bone Healing in intramedullary nailing through
Mechanical Stimulation
Stabilization technique:
External fixationTibia diaphysis fractures is the one in which
healing is most difficult Plating
www.synthes.com
www.synthes.com
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Intramedullary nailing
Fixation stability and healing
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Improvement of intramedullary nailing system
Understanding of bone-nail fixation system mechanics
Demands
How the implant guaranties fracture stability and bone aligment;How it is conducive to bone regeneration
Biomechanical stability of the whole bone
Compare to
Fixation stability and healing
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Methodology
MechanicalExperimentation
Finite Element Analysis (FEA)
VALIDATE
EXTEND
Whole bone stiffnessvs
Bone-intramedullary nail Stiffness
Interfragmentary movements
3D Scan
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
SolidWorks ANSYS®
Methodology
• Cortical and trabecular bone structures boundary definition;
• Solid model construction;
• Surface preparation;• External surface
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Methodology: Whole bone system
Neto et al. Rev Hosp Clín. 54, 1999
SawBones®
Image obtained from: Heiner et al. J Biomech 34, 2001 and adapted with
data from SawBones®
Heinonen et al. Bone 29, 2001
Tencer A. Biomechanics of Fixation and Fractures (Book chapter), 2006
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Methodology: Whole bone system
3D Scan
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
SolidWorks ANSYS®
Methodology
• Grips design
• Cortical and trabecular bone structures boundary definition;
• Solid model construction;
• Surface preparation;• External surface
Dailey et al. Clin Biomech 27, 2009Penzkofer et al. Arch Orthop Trauma Surg 129, 2009
Augat et al. J Orthop Trauma 22, 2008
“The long axis of each specimen is aligned parallel to the base plate of the machine”
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Methodology: Containers/grips
“Tibiae were oriented vertically”Heiner et al. J Biomech 34, 2001Heiner et al. J Biomech 41, 2008
“A set of reference axes (bone coordinate system), was marked on the surface of the tibia to help align the bone during experiments and to correlate the experiments with the FE model”
Gray et al. Proc Inst Mech Eng 221, 2007Gray et al. J Biomech Eng 130, 2008
Vertical axis
Anatomical axis
Mechanical axis
Sagittal plane
Coronal plane
c
Yoshioka et al. J Orthop Res 7, 1989
Adapted from: Han et al. Knee Surg Sports Traumatol
Arthrosc, 2008
Tibial mechanical axis
c
o o
Pickering et al. J Bone Joint Surg, 2012
Sagittal plane Coronal plane
Yoshioka et al. J Orthop Res 7, 1989
Tibial plateau
Distal tibia
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
• All loading modes;• The same tibia alignment
guaranteed in both simulation and mechanical experimentation;
• Avoid potting bone specimens in cement;
• Misalignment of bone;
Methodology: Containers/grips
3D Scan
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
SolidWorks ANSYS®
Methodology
• Grips design
• Intramedullary nail implantation in the bone
• Intramedullary nail structure drawing
• Cortical and trabecular bone structures boundary definition;
• Solid model construction;
• Surface preparation;• External surface
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Bone-implant complex (BIC) - Nail
Harmonic Experimental(Hz)
Simulation - Ansys®(Hz) Error (%)
1st 384 388.11 7.6
2nd 432 427.3 5.5
3rd 1057 1047.1 6.4
Validation through free-free boundary condition
• L.A. Medical M596222 AB0366 T• nail (inches)• Circular ring cross section (inner diameter 5 mm/
0.197 inches) • Stainless steel - AISI 316L ASTM F318
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Bone-implant complex (BIC) – Nail implantationwww.aofoundation.org
Han et al. Knee Surg Sports Traumatol
Arthrosc, 2008
ReamingCreation of the nail entry site Nail inserted Nail locking
• Diameter: 12.7 mm (0.5 inches)• Length: 60 mm (2.36 inches)
To accommodate the larger proximal portion in the nail
Tibial anatomical axis
7 cm(2.75 inches)
7 cm(2.75 inches)
11 mm reaming (0.43 inches)
The correct position of the nail was validated by an experienced orthopedic
surgeon
• Proximally: 2 screws• Distally: 2 screws• Locking mode• No play between the screw and
the bone
3D Scan
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
SolidWorks ANSYS®
Methodology
• Grips design
• Intramedullary nail implantation in the bone
• Intramedullary nail structure drawing
• Cortical and trabecular bone structures boundary definition;
• Solid model construction;
• Surface preparation; • Finite element analysis• External surface
Intramedullary Nailing Stability in the Bone Healing Process
Concept
Nature has optimize this process and it would be difficult to intervene in order to improve fracture healing
Horn et al. Injury Int J Care Injured 40, 2009
There is a tendency to modify the locking option for better stability
High bone-implant stability and instability are detrimental for bone healing
Improve treatment method for bone fracture repair by reducing the patient healing time
Bailón-Plaza et al. J Biomech 36, 2003
Beneficial effects of early loading and adverse effects of delayed loading on bone healing
There is never been determine a quantifiable relationship between the rate of healing and mechanical
Comiskey et al. J Biomech 43, 2010
Granulation tissue … Woven bone REPAIR REMODELING
Load Whole boneBIC
FE Penzkofer et al. (2009)Axial compression in N/μm 13400 1250 723 ± 421
Torsion (IR) in Nm/deg 8.9 4.5 0.8 ± 0.14-Point Bending (AT) in Nm2 146.2 51.2 37 ± 84-Point Bending (LT) in Nm2 87.08 57.6 37 ± 9
Shear (Saggital) in N/mm - 294.1 131 ± 30Shear (Coronal) in N/mm - 309.6 164 ± 89
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Axial compression:Torsion:4-Point Bending (AT):4-Point Bending (LT):Shear (Saggital):Shear (Coronal):
11 µm
Intact bone
214 µm0.36 deg 0.58 deg0.12 mm0.12 mm
0.32 mm0.36 mm
-- 0.68 mm
0.65 mm
=1.95%
Regression line:Load/moment--deformation/rotation curve
Evaluated/validade: Heiner et al. J Biomech 41, 2008
Horn et al. (2009)620 ± 240 (CL) 1420 ± 421 (ASL)
Fracture location: CentralLoad: 100 NNail diameter: 9 mmFracture gap width: 8 mmConventional nails
Results
0.3 – 0.8% Minimal mechanical stimulationBailón-Plaza et al. J Biomech 36, 2003
Fritton et al. (2000) Rubin et al. (2001)Goodship et al. (2009)
Low-magnitude, high-frequency mechanical signals ability to influence fracture healing
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
Conclusions
Difficult to compare studies due to non-standard experimental set-up
High-frequency low-amplitude interfragmentary micromotion regime applied during early healing recovery phase may be an interesting strategy to enhance the rate and quality of bone repair without risking the disruption of the healing process
An ideal implant stiffness design demands an extensively understanding of the complex relation between the mechanical stimulus (type, magnitude, rate, duration and timing of initiation of loading) and the bone healing process
Validation of the finite element model through mechanical experimentation is essential
Nailing Stability during Tibia Fracture Early Healing Process: A Biomechanical Study
We would like to thank Portuguese Foundation for Science and Technology (FCT)
Luso-American Development Foundation (FLAD)
and alsoInternational Conference and Expo on Biomechanics and Implant Design for giving the opportunity to present the work developed